The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Operating an engine with a partially closed throttle results in undesirable pumping losses. However, an engine operating at substantially wide open throttle results in decreased fuel efficiency and increased emissions due to an increased combustion rate. The increased combustion rate also used provides a torque increase. It is known to control the engine combustion rate and increase fuel efficiency by using residual burned gases to dilute the unburned gas mixture. Dilution exists in the unburned gas mixture because the already burned residual gases reduce the peak burned gas temperature and decrease the combustion rate and resulting engine torque.
It is known, for example, to use a cam phaser to modulate a cam overlap condition between intake and exhaust valves, wherein the valve overlap condition controls the amount of dilution in the unburned gas mixture. When the valve overlap condition is increased, dilution provided by the residual burned gases also increases. However, cam phasers incorporating existing hydraulic systems are responsively slow. The slow response rate of hydraulic system cam phasers creates a time-lag difference between an output torque request provided by an operator's input to an accelerator pedal and the controlled input torque of the engine. In a hybrid transmission an electric machine will provide motor torque, in addition to input torque, for generating an output torque to meet the output torque request. Electric cam phasers are fast enough for transient control, but too expensive. There exists a need for a control system in a hybrid transmission for increasing the time-lag difference between a user output torque request and input torque controlled by cam phasing.